U.S. patent number 7,210,932 [Application Number 10/376,375] was granted by the patent office on 2007-05-01 for pin-tray dental prostheses modeling system.
Invention is credited to Richard Barnes, Jerry P. Honstein, Anthony Siragusa.
United States Patent |
7,210,932 |
Honstein , et al. |
May 1, 2007 |
Pin-tray dental prostheses modeling system
Abstract
A dental prostheses modeling system includes a tray having in an
upper part thereof a trough for receiving a semi-liquid modeling
material or casting material such as plaster of Paris or die stone,
the trough having opposed vertical walls in which are formed
alternating vertically disposed ribs and grooves for forming
complementary shapes in sides of a casting molded in said tray, a
base portion of which has in outer walls thereof alternating
vertically disposed grooves and ribs, the trough having a frangible
base plate which overlies an upwardly concave cavity for receiving
liquid die stone after the upper casting has solidified, hardened
and been removed, the base plate being broken and removed to
uncover an elongated aperture joining the upper trough to the lower
cavity enabling the cast to be ejected from the tray, pins fitted
into selected portions of the casting base, the casting reinserted
into the trough, and the tray inverted to receive liquid die stone
which hardens to form a stone base matrix for insertably receiving
pins protruding downwardly from portions of the casting, the
casting being then removed from the trough in the upper portion of
the tray and severed into segments which are releasably
re-engageable along with adjacent portions of the casting within
the tray, proper registration between segments of the casting being
effected by insertable receipt of pins within holes formed in the
die stone base during hardening thereof, and engagement between
ribs and grooves of the casting segments with
complementarily-shaped grooves and ribs in the inner side walls of
the upper tray trough.
Inventors: |
Honstein; Jerry P. (Corona,
CA), Barnes; Richard (Mission Viejo, CA), Siragusa;
Anthony (Anaheim, CA) |
Family
ID: |
32869091 |
Appl.
No.: |
10/376,375 |
Filed: |
February 26, 2003 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20040166465 A1 |
Aug 26, 2004 |
|
Current U.S.
Class: |
433/60; 433/57;
433/64; 433/74 |
Current CPC
Class: |
A61C
9/002 (20130101); A61C 11/02 (20130101) |
Current International
Class: |
A61C
11/00 (20060101) |
Field of
Search: |
;433/34,74,213,60,54 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: O'Connor; Cary E.
Assistant Examiner: Stokes; Candice C.
Attorney, Agent or Firm: Chapin; William L.
Claims
What is claimed is:
1. A method for making a dental prostheses model cast including a
base and a cast of teeth made from an impression mold having formed
therein imprints of a patient's teeth, said method comprising; a.
pouring liquid die stone into a shallow upper depression in a
molding tray having, i. a body having therewithin an interior space
enclosed by an inner longitudinally disposed surface of a
peripheral wall disposed between an upper transverse face and a
lower transverse face, ii. a base wall located within said interior
space of said body, said base wall having an upper surface recessed
inwardly to a first, upper recess depth inwardly of said upper
transverse face and forming within said interior space a first,
downwardly concave shallow upper depression, said base wall having
a lower surface recessed inwardly a second, larger recess depth
inwardly of said lower transverse face, and forming a second,
upwardly concave lower depression which is deeper than said upper
depression, said base wall having formed therein a central panel
breakable away from an outer ring-shaped portion of said base wall
to form therethrough an aperture which communicates between said
upper and lower depressions, iii. a plurality of spaced apart
projections which protrude inwardly form inner surfaces of opposed
inner sides of said peripheral wall, said projections alternating
with spaces formed between said projections, iv. said shallow upper
depression being adapted to receive liquid die stone therein to
thereby harden to comprise a base of a dental model cast fused with
a cast of teeth made in an impression mold, said central panel of
said base wall adapted to being broken away from said outer
ring-shaped portion of said base wall, and enabling said cast to be
ejected upwardly out from said tray, pins installed on a lower
surface of said cast base, said cast base being re-insertable into
said shallow upper depression to a predetermined index position
within said tray determined by engagement of said alternating
projections and spaces of said tray with complementary-shaped
spaces and projections molded into sides of said cast, said recess
depth of said lower depression being greater than extension length
of said pins below said cast, a. allowing time for said liquid die
stone to harden, b. breaking said central panel away from said
outer ring-shaped portion of said base wall, c. ejecting said cast
base upwardly from said tray, and e. installing pins protruding
downwardly from a lower face of said cast base.
2. The method of claim 1 wherein said molding tray is further
defined as including at least one pair of abutment flanges which
protrude outwardly from opposite locations of an outer side of said
peripheral wall.
3. The method of claim 2 further including using a dental
prostheses modeling apparatus including the molding tray of claim
2, and force applying means for applying a compressive force on
said flanges relative to said center panel of said base wall
sufficient to break said center panel away from said outer
ring-shaped portion of said base wall.
4. The method of claim 3 wherein said force applying means is
further defined as comprising in combination, a template including
a base having protruding upwardly from an upper surface thereof a
lug having an upper surface for abutting a lower surface of said
center panel, and a knowck-out tool for exerting a downward force
on said abutment flanges relative to said template lug.
5. The method of claim 1 further including utilizing releasable
attachment means for releasably attaching said tray to a second of
said trays.
6. The method of claim 5 wherein said releasable attachment means
is further defined as comprising in combination a bracket
protruding outward from a said wall of said body, and hinge
mechanism means for pivotably coupling
7. A method for making a dental prostheses model cast including a
base and a cast of teeth made from an impression mold having formed
therein imprints of a patient's teeth, said method comprising; a.
pouring liquid die stone into a shallow upper depression in a
molding tray having, i. a body having therewithin an interior space
enclosed by an inner longitudinally disposed surface of a
peripheral wall disposed between an upper transverse face and a
lower transverse face, ii. a base wall located within said interior
space of said body, said base wall having an upper surface recessed
inwardly to a first, upper recess depth inwardly of said upper
transverse face and forming within said interior space a first,
downwardly concave shallow upper depression, said base wall having
a lower surface recessed inwardly a second, larger recess depth
inwardly of said lower transverse face, and forming a second,
upwardly concave lower depression which is deeper than said upper
depression, said base wall having formed therein a central panel
breakable away from an outer ring-shaped portion of said base wall
to form therethrough an aperture which communicates between said
upper and lower depressions, iii. a plurality of spaced apart
projections which protrude inwardly form inner surfaces of opposed
inner sides of said peripheral wall, said projections alternating
with spaces formed between said projections, a. allowing time for
said liquid die stone to harden, b. breaking said central panel
away from said outer ring-shaped portion of said base wall, c.
ejecting said cast base upwardly from said tray, and e. installing
pins protruding downwardly from a lower face of said cast base, and
f. inverting said tray with said cast positioned thereon, pouring
liquid die stone into said deeper lower impression, g. allowing
time for said die stone in said lower depression to harden, thereby
form a boase matrix and whereby said cast base is repeatedly
removable from said tray, said cast base being re-insertable into
said molding tray to a precisely predetermined index position
within said tray determined by cooperative active of said
projection and spaces of said tray with complementary-shaped spaces
and projections molded into sides of said cast base, and said pins
received in complementary-shaped cavities in said base matrix.
8. The method of claim 7 wherein said molding tray is further
defined as including at least one pair of abutment flanges which
protrudes outwards from opposite locations of an outer side of said
peripheral walls.
9. The method of claim 7 further including using a drilling
alignment fixture which facilitates making bores for pins into a
base of a cast molded in said tray without said cast from said
tray, said drilling alignment fixture comprising an elongated body
having a lower wall and an upper surface in which is formed an
elongated channel adapted to receive said tray containing therein
said cast, a drill guide bushing through said lower wall of said
body, and an index line longitudinally aligned with the bore center
line of said drill guide bushing, said index line being inscribed
on outer wall surfaces of said body, whereby said tray and cast may
be moved longitudinally on said body of said alignment fixture to
position a desired part of said cast in alignment with said index
line, and a drill inserted through said bore of said drill guide
and rotated to drill a pin bore into said cast of said base at said
location.
10. The method of claim 7 further including utilizing releasable
attachment means for releasably attaching said tray to a second of
said trays.
11. The method of claim 10 wherein said releasable attachment means
is further defined as comprising in combination a bracket
protruding outward from a side wall of said body, and hinge
mechanism means for pivotably coupling said tray to a second tray
in place perpendicular to said upper edge wall surface of said
body.
12. A molding tray for use in making a dental prostheses model from
an impression mold having formed therein imprints of a patient's
teeth, said molding tray comprising; a. a body having therewithin
an interior space enclosed by an inner longitudinally disposed
surface of a peripheral wall disposed between an upper transverse
face and a lower transverse face, b. a base wall located within
said interior space of said body, said base wall having an upper
surface recessed inwardly to a first, upper recess depth inwardly
of said upper transverse face and forming within said interior
space a first, downwardly concave shallow upper depression, said
base wall having a lower surface recessed inwardly a second, larger
recess depth inwardly of said lower transverse face, and forming a
second, upwardly concave lower depression which is deeper than said
upper depression, said base wall having formed therein a central
panel breakable away from an outer ring-shaped portion of said base
wall to form therethrough an aperture which communicates between
said upper and lower depressions, c. a plurality of spaced apart
projections which protrude inwardly form inner surfaces of opposed
inner sides of said peripheral wall, said projections alternating
with spaces formed between said projections, d. said shallow upper
depression being adapted to receive liquid die stone therein to
thereby harden to comprise a base of a dental model cast fused with
a cast of teeth made in an impression mold, said central panel of
said base wall adapted to being broken away from said outer
ring-shaped portion of said base wall, and enabling said cast to be
ejected upwardly out from said tray, pins installed on a lower
surface of said cast base, said cast base being re-insertable into
said shallow upper depression to a predetermined index position
within said tray determined by engagement of said alternating
projections and spaces of said tray with complementary-shaped
spaces and projections molded into sides of said cast base, said
cast and tray inverted, and liquid die stone poured into said
deeper lower depression of said tray to form upon hardening a base
stone matrix for releasably receiving said pins protruding
downwardly from said base of said cast, e. at least one pair of
abutment flanges which protrude outwards from oppose sides, and f.
a drilling alignment fixture which facilitates making bores for
pins into a base of a cast molded in said tray without removing
said cast from said tray, said drilling alignment fixture
comprising an elongated body having a lower wall and an upper
surface in which is formed an elongated channel adapted to receive
said tray containing therein said cast, a drill guide bushing
through said lower wall of said body, and an index line
longitudinally aligned with the bore ecenter line of said drill
guide bushing, said index line being inscribed on outer wall
surfaces of said body, whereby said tray and cast may be moved
longitudinally on said body of said alignment fixture to position a
desired part of said cast in alignment with said index line, and a
drill inserted through said bore of said drill guide and rotated to
drill a pin bored into said cast of said base at said location.
13. A method for making a dental prostheses model cast including a
base and a cast of teeth made from an impression mold having formed
therein imprints of a patient's teeth said method comprising; a.
pouring liquid die stone into a shallow upper depression in a
molding tray having, i. a body having therewithin an interior space
enclosed by an inner longitudinally disposed surface of a
peripheral wall disposed between an upper transverse face and a
lower transverse face, ii. a base wall located within said interior
space of said body, said base wall having an upper surface recessed
inwardly to a first, upper recess depth inwardly of said upper
transverse face and forming within said interior space a first,
downwardly concave shallow upper depression, said base wall having
a lower surface recessed inwardly a second, larger recess depth
inwardly of said lower transverse face, and forming a second,
upwardly concave lower depression which is deeper than said upper
depression, said base wall having formed therein a central panel
breakable away from an outer ring-shaped portion of said base wall
to form therethrough an aperture which communicates between said
upper and lower depressions, iii. a plurality of spaced apart
projections which protrude inwardly form inner surfaces of opposed
inner sides of said peripheral wall, said projections alternating
with spaces formed between said projections, b. allowing time for
said liquid die stone to harden, c. breaking said central panel
away from said outer ring-shaped portion of said base wall, d.
ejecting said cast base upwardly from said tray, e. installing pins
protruding downwardly from a lower face of said cast base, and f.
inverting said tray with said cast positioned thereon, pouring
liquid die stone into said deeper lower impression, g. allowing
time for said die stone in said lower depression to harden, thereby
form a base matrix and whereby said cast base is repeatedly
remoable form said tray, said cast base being re-insertable into
said molding tray to a precisely predetermined index position
within said tray determined by cooperative action of said
projection and spaces of said tray with complementary-shaped spaces
and projections molded into sides of said cast base, and said pins
received in complementary-shaped cavities in said base matrix, and
h. using a drilling alignment fixture which facilitates making
bores for pins into a base of a cast molded in said tray without
removing said cast from said tray, said drilling alignment fixture
comprising an elongated body having a lower wall and an upper
surface in which is formed an elongated channel adapted to receive
said tray containing therein said cast, a drill guide bushing
through said lower wall of said body, and an index line
longitudinally aligned with the bore center line of said drill
guide bushing, said index line being inscribed on outer wall
surfaces of said body, whereby said tray and cast may be moved
longitudinally on said body of said alignment fixture to position a
desired part of said cast in alignment with said index line, and a
drill inserted through said bore of said drill guide and rotated to
drill a pin bore into said cast of said base at said location.
Description
BACKGROUND OF THE INVENTION
A. Field of the Invention
The present invention relates to articles and methods used in the
fabrication of dental prostheses such as crowns and bridges made of
various combinations of metal and ceramic materials and used to
overlie or replace imperfect or missing teeth. More particularly,
the invention relates to a system for use in fabricating crowns and
bridges, the system including an apparatus and method for making
from a mold or impression of a patient's teeth, a dental model cast
which is formed from solidified liquid die stone poured into the
mold. The dental model cast is segmentable into die segments, each
of which has both horizontally protruding ribs and grooves for
releasably engagement with complementary-shaped grooves and ribs
formed in a support tray, and a pin protruding downwardly from the
die segment and adjacent segments for receipt within indexing holes
formed through a base member matrix formed within the tray, the pin
facilitating gripping and manipulating of the die during various
fabrication operations performed by a dental technician.
B. Description of Background Art
A dental procedure which is routinely used to restore function and
aesthetic appearance to a person's mouth after a tooth has become
broken, structurally degraded by disease or removed entirely,
consists of capping or replacing the tooth with a prosthetic
restoration, such as a crown or bridge. One form of dental
prosthesis or artificial tooth replacement which is widely used
consists of a cap or crown for a tooth that is made of a resin,
molded ceramic material, a precious metal such as gold or an alloy
thereof, or a layered combination of metals and resins or ceramic
materials. Various combinations of the foregoing materials provide
tooth restorations which possess requisite durability and aesthetic
appearance, as well as sufficient hardness to be suitable for
chewing foods. The process of fabricating tooth restorations has
been in use for a substantially long time, and includes a
well-defined sequence of steps, which are briefly summarized
below.
According to a first step in existing methods of fabricating dental
prostheses or artificial replacement teeth, a negative impression
mold is made of a group of a patient's teeth, including missing,
broken or decayed teeth which are to be repaired or replaced and
teeth which are laterally adjacent to the defective teeth. Such
impressions are typically made by positioning within the mouth of a
patient, adjacent to teeth to be restored, a shallow curved tray
which contains a polymer material such as alginate, elastomer,
hydrocolloid or a polyether, which is capable of being indented by
a tooth, and forming and retaining a stable impression of the
tooth. The impression material is initially in the form of a putty,
slurry or thick paste which rapidly solidifies at ambient room
temperature and pressure. The tray is inserted into a patient's
mouth positioned generally horizontally and in vertical alignment
with a subject area of the teeth, and the patient bites down on the
tray, or the tray is pressed into contact with the teeth, thus
pressing the teeth into the viscous semi-liquid mold impression
material held by the tray. After a few minutes, the mold impression
material solidifies into a rubber-like elastomeric state which has
formed therein precise negative impressions of teeth in a subject
area of the patient's mouth.
Dental impression trays for use as described above are available in
a variety of styles. One type tray has an arcuately curved
plan-view shape which is similar to the curved arrangement of teeth
in the jaw. The curved arc length of the tray approximates that of
about one half an upper or lower jaw and hence is referred to as a
quadrant tray. A flat, paddle-like handle protruding horizontally
outwards from one end of the tray is usually provided, to
facilitate inserting and removing the tray from a patient's mouth.
A typical quadrant tray has on one side thereof a curved trough for
receiving impression mold material, may be used to make impressions
of upper or lower jaw quadrants and is referred to as a standard
quadrant or single-bite tray.
Since an important structural feature of a dental prosthesis is
proper registration and biting contact or occlusion between the
prosthesis and teeth located in the opposing jaw, it is desirable
to make an impression of occluding teeth in the opposing jaw in
addition to the impression made of teeth that are to be restored.
Therefore, it has been a trend in dentistry for the dental
professional to simultaneously make impressions of teeth that are
to be restored and occluding teeth in the opposing jaw. A
convenient method for simultaneously making restorative and
opposing impressions utilizes a tray which has a plan-view shape
similar to that of a single-bite, standard quadrant impression
tray, but which has upper and lower troughs for holding mold
impression material in both upper and lower sides of the tray. Both
the upper and lower troughs of these "double-bite" or "triple"
trays are filled with viscous impression material and inserted into
the patient's mouth between the upper and lower jaws in vertical
alignment with teeth to be restored, whereupon the patient bites
down on the tray, simultaneously forming impressions of upper and
lower teeth.
After impressions of teeth have been made in the manner described
above, and the mold impression material solidified, the tray
holding solidified mold impression material containing negative
impressions of a patient's teeth is removed. The mold, typically
referred to as an "impression," is then used to make positive
replicas of teeth by pouring a semi-liquid molding material such as
plaster of Paris, or die stone, into the depressions formed in the
impression, which are accurate negative replicas of the teeth.
After the die stone has solidified into a hard stone-like casting,
or cast, the cast is removed from the impression, a task which is
facilitated by the fact that the impression material is
elastomeric, enabling it to be readily peeled away from the die.
The casting is then used to fabricate one or more tooth
restorations or prostheses in the following manner.
A master cast, i.e., a cast which includes replicas of teeth which
are to be restored, is partitioned into one or more individual
segments and/or dies, each consisting of a replica of a tooth which
is to be replaced by or fitted with a dental prosthesis.
Partitioning of a master cast into die segments is typically
accomplished by making parallel vertical saw cuts through the
master cast. The individual die segment or segments are then used
as three-dimensional models or templates for fabricating crowns or
bridges. In general, the exterior surfaces of the prosthesis cannot
simply replicate those of the die segments. This is because the
occlusal surface of the prosthetic tooth restoration, and to a
lesser extent, lateral surfaces of the restoration, may require
contouring which is different from that of the die segment. For
example, the process of fabricating crowns for diseased or damaged
teeth entails grinding decayed or broken outer portions of the
tooth down until a stump of healthy dentin or enamel remains, a
procedure referred to as "prepping" the tooth. Obviously, a crown
which is fabricated to fit onto a stump must have a substantially
different, tooth-like shape rather than a stump-like shape.
From the foregoing discussion, it can be appreciated that the
fabrication of dental prosthesis models from die segments is a
labor-intensive task requiring the skills of a prosthodontist or
skilled, experienced, dental lab technician. Fabrication of
prosthetic dental models typically requires that die segments be
contoured by applying a workable material to exterior portions of
the die segment, and sculpting the material. The die segment is
then replaced into the space in the master cast from which it has
been removed, and proper occlusion of the sculpted prosthetic model
confirmed by bringing model teeth replicated in the opposing cast
into bite-like contacting registration with the occlusal surfaces
of the prosthetic model and adjacent teeth replicas of the master
cast. This registration check, generally must be repeated several
times, to ensure proper sculpting of the occlusal surface of the
die segment which serves as a model for fabricating a dental
prosthesis. Moreover, it is essential that the biting contact or
occlusion between the teeth replicated by the master cast and
opposing cast precisely duplicate occlusion of the patient's teeth.
Therefore, the master cast and opposing cast must be precisely and
repetitively pivotably contacted against one another in a motion
which simulates the opening and closing of a patient's jaws. Upon
satisfactory completion of sculpting of lateral and occlusal
surfaces of die segments, the die segment is used as a mold pattern
for casting a metal, ceramic, or metal-ceramic composite dental
prosthesis.
One type of device which is used to pivotably register master and
opposing dental models or arches is referred as an articulator. For
example, Cho, U.S. Pat. No. 6,019,601, Tray Modeling System With
Articulator Assembly And Ejection Mechanism For Producing A Dental
Model, discloses a pair of trays which are removably and pivotably
joined together by detachable hinge members. Each tray has formed
upon an upper surface thereof a rectangularly-shaped, trough-like
depression, the longest inner facing side walls of the trough
having formed therein alternating vertically disposed ribs and
grooves. The device is used by pouring a thick paste of liquid die
stone slurry into both a dental impression and the tray, and
inverting the impression to enable the liquid die stone slurries in
the impression and tray to commingle. When the die stone has
solidified, the impression is removed from the cast, and the cast
removed from the tray by punching through a frangible base panel in
the tray, forcing the cast vertically outwards from the trough. The
cast is then sawed into segments, which are returnable to precisely
repeatable locations within the trough because of the interlocking
ribs and grooves formed in the vertical walls of the cast by die
stone solidifying in the grooves and ribs, respectively, of the
trough side walls, during hardening of the die stone. In the same
manner, an opposing cast is made in the other tray, and the trays
pivoted towards one another on the hinge pins to precisely and
repeatedly bring the occlusal surfaces of the opposing cast and
master cast into occlusal registration.
The Cho modeling system and articulator provides a convenient means
for preparing and articulating dental models. However, some dental
technicians prefer working with die segments which have an
elongated cylindrical pin protruding from the base of the die
segment. In modeling systems using pinned die segments, the pins
are insertably received in holes provided in the base of a tray,
and are used to reproducibly position or relate individual die
segments to adjacent portions of the master cast. Moreover, a pin
protruding from a die segment provides a convenient handle which
enables the dental technician to hold a die segment while working
on it, including rotating the die segment a full 360 degrees by
twisting the die segment pin between the thumb and forefinger of
the dental technician. Thus, Sim, U.S. Pat. No. 6,402,513, Dental
Model Articulator, discloses a dental model articulator which has
pinned die segments. The dental model articulator disclosed in Sim
utilizes a top insert which has front and rear upwardly protruding
ridges that have grooved upper surfaces. The insert is detachably
supported on a lower frame. To pour a master cast of a dental
impression, a middle frame must be fastened to a lower frame and
around the top insert by engaging slots on left and right sides of
the middle frame with retentive latches which protrude upwards from
the lower frame, on left and right sides of an upper opening in the
lower frame which holds the top insert. According to the disclosure
of Sim, the middle frame is discarded after completion of a second
pour of liquid die stone through a bottom opening of lower frame,
to form a perforated matrix for receipt of pins installed in the
base of the first impression casting. The grooved insert is
discarded after the first pour.
The present invention was conceived of to provide an improved
dental prostheses modeling system which utilizes die segments that
each have ribs and grooves which enable repeatable removal from and
re-registration of segments within a cast. Each die, segment also
has a downwardly protruding pin for facilitating both manipulation
of the die segment and reinsertion into the cast, the die segment
being quickly and easily fabricated using a sparse number of
components and steps.
OBJECTS OF THE INVENTION
An object of the present invention is to provide a dental
prostheses modeling system for fabricating models of human teeth
from impressions made thereof.
Another object of the invention is to provide a dental prostheses
modeling system which includes a tray having in an upper part
thereof a trough for receiving a semi-liquid modeling material or
casting material such as plaster of Paris or die stone, the trough
having opposed vertical walls in which are formed alternating
vertically disposed ribs and grooves for forming a casting, a base
portion of which has in outer walls thereof alternating vertically
disposed grooves and ribs, the trough having a frangible base plate
which overlies an upwardly concave cavity for receiving liquid die
stone after the upper casting has solidified and been removed, the
base plate being broken and removed to uncover an elongated
aperture joining the upper trough to the lower cavity, enabling the
casting to be pushed upwardly out of the tray, pins fitted into
selected portions of the casting base, the castings reinserted into
the trough, and the tray inverted to receive liquid die stone which
hardens to form a stone base matrix for insertably receiving pins
protruding downwardly from portions of the casting, the casting
being then removed from the trough in the upper portion of the tray
and severed into segments which are releasably re-engageable along
with adjacent portions of the casting within the tray, proper
registration between segments of the casting being effected by
insertable receipt of pins within holes formed in the die stone
base during hardening thereof, and engagement between ribs and
grooves of the casting segments with complementarily-shaped grooves
and ribs in the inner side walls of the upper tray trough.
Another object of the invention is to provide a dental prostheses
modeling system which includes a pair of upper and lower trays for
use in molding from liquid die stone bases for cast dental models
of upper and lower teeth from impressions thereof, the trays being
hingedly joinable to enable master and opposing dental castings
formed in the trays to pivotably contact one another to ascertain
proper occlusion between surfaces of teeth modeled by the master
and opposing casts, each tray having in an upper part thereof a
trough having formed in inner facing walls thereof altemabng
inwardly projecting ribs and grooves, the trough having a frangible
base plate which may be pushed upwardly to cause it to break and
eject a hardened dental model casting base from the tray, whereupon
vertically downwardly disposed pins may be installed in the bases
of selected segments of the casting, the casting replaced in the
trough with the pins, now coated with a release agent, protruding
downwardly through the opening left by removal of the frangible
base plate, and liquid die stone poured into a concave lower
portion of the inverted tray to form upon hardening a base stone
matrix having holes formed through its thickness dimension by the
pins, whereupon the casting may be removed from the upper trough
portion of the tray, and segmented by vertical cuts into a desired
number of die segments each having a pin protruding downwardly from
its base, and the die segments releasably replaced in the tray in
precise relative relationship because of indexing provided by the
die segment pins being insertably received in corresponding holes
in the base die stone matrix, and engagement between vertically
disposed ribs and grooves molded in the sides of the casting with
corresponding grooves and ribs in the inner facing walls of the
trough.
Various other objects and advantages of the present invention, and
its most novel features, will become apparent to those skilled in
the art by perusing the accompanying specification, drawings and
claims.
It is to be understood that although the invention disclosed herein
is fully capable of achieving the objects and providing the
advantages described, the characteristics of the invention
described herein are merely illustrative of the preferred
embodiments. Accordingly, we do not intend that the scope of our
exclusive rights and privileges in the invention be limited to
details of the embodiments described. We do intend that
equivalents, adaptations and modifications of the invention
reasonably indexable from the description contained herein be
included within the scope of the invention as defined by the
appended claims.
SUMMARY OF THE INVENTION
Briefly stated, the present invention comprehends a system which
includes an apparatus and method for fabricating models of human
teeth; the models are subsequently used in the fabrication of
dental prostheses such as crowns and bridges made of various
combinations of metal and ceramic materials and used to overlie or
replace imperfect or missing teeth. According to the invention,
methods and apparatus are provided for making dental impression
casts which are segmentable into die segments for use as models in
fabricating dental prostheses.
According to one aspect of the invention, a molding tray for
molding the base of a dental model cast has a longitudinally
elongated rectangular plan view shape, and has formed in opposed
inner vertically disposed longitudinal perimeter walls thereof
horizontally outwardly protruding protrusions altemating with
horizontally inwardly protruding depressions. Complementary-shaped
depressions and protrusions are formed in opposed inner facing
walls of the base of a dental model cast formed from solidified
liquid die stone poured into the tray. According to the invention,
the tray includes a horizontally disposed, frangible base plate
which is located between upper and lower surfaces of the tray, thus
forming with vertical perimeter walls of the tray upper and lower
shallow, rectangular plan view upper and lower depressions or
troughs. The frangible base plate serves as a support base for
pouring a base for a dental model casting within the upper trough
in the upper portion of tray. Semi-liquid die stone is poured to
overflowing into a dental impression mold containing imprints of a
patient's teeth and poured to overflowing into the upper opening of
the upper trough in the upper portion of the tray. The filled
impression is then inverted, positioned over the tray, and pressed
down into semi-liquid die stone in the tray. The liquid die stone
in the impression and tray co-mingle, eventually hardening to form
a unitary cast comprising a base portion molded in the tray and an
upper portion which replicates teeth which imprinted the impression
mold. After the cast has hardened, an upwardly directed force is
exerted on the underside of the frangible base plate, breaking the
base plate and ejecting the hardened cast upwardly out of the tray.
The hardened cast is then inverted, and blind bores are drilled
into the lower surface of the inverted base of the cast, the bores
being positioned in vertical alignment with cast replicas of
selected teeth which are to serve as models for fabricating
individual dental prostheses. Cylindrically-shaped pins are then
inserted into the bores, and the cast is then flipped over to an
upright position, with pins protruding perpendicularly downwards
from the base of the cast, and reinserted into the upper opening of
the tray. Ribs and grooves molded into opposite longitudinally
disposed vertical sides of the cast base vertically slidably engage
with complementary-shaped grooves and ribs in the inner side walls
of the tray which formed the ribs and grooves of the cast. This
arrangement ensures that the cast is returned to a previously
predetermined lateral index position relative to the horizontal
tray perimeter. Moreover, the cast is returned to a previously
predetermined vertical position within the tray by abutting contact
between the lower surface of the base of the cast and a flat
rectangular ring-shaped upper edge wall of the tray. The tray and
inserted cast are then inverted, with the casting secured from
falling out of the tray by a preferred method described below.
Liquid die stone is then poured into the lower opening of the lower
trough in the lower portion of the tray to a level between the
lower edge of the tray and the downwardly protruding ends of the
indexing pins, which are coated with a liquid release agent before
pouring the die stone. Liquid die stone within the lower tray
trough is then allowed to harden, forming a stone base matrix. An
upwardly directed force is then exerted on the bottom surface of
pins protruding from the stone base matrix, thereby pushing the
cast upwardly out of the tray. The cast is then segmented into
individual die segments for modeling individual dental prostheses,
by making one or more saw cuts vertically through the cast,
adjacent to a selected die segment. Individual die segments are
once again reinserted into the upper opening of the tray, to
thereby re-assemble a complete cast comprised of individual die
segments and adjacent portions of the cast within the tray.
Placement of the pinned die segments within the tray is facilitated
by initial approximate alignment of mating ribs and grooves in the
inner sides of the tray and the outer sides of the die segment
effected by partial insertion of a die segment pin into the upper
opening of a corresponding pin bore through the stone base matrix
in the lower part of the tray. The combined aligning forces
provided by insertion of a pin into a pin bore, and subsequent
inserting of ribs of the casting base into tray grooves, enables
individual die segments to be quickly and easily removed from the
tray, subjected to various prosthesis modeling operations, and
returned to a precisely repeatable, indexed position within the
cast, as many times as is required.
A preferred embodiment of a pin tray modeling system according to
the present invention includes an opposing tray for making a
casting of a dental impression which was made of teeth opposed to
those which are to be fitted with prostheses. The preferred
embodiment also includes components which hingedly couple a master
tray holding a master impression cast to an opposing tray holding
an opposing impression cast and forming therewith an articulator
mechanism which enables the occlusal surfaces of the master and
opposing casts to be brought into pivotable contact with one
another, thereby simulating closure of a patient's jaws and proper
occlusion of the teeth modeled in the two casts. If dental
prostheses are required only for one jaw, the cast made of the
opposing jaw does not have to have removable die segments.
Therefore, the opposing tray need not be provided with the
previously described structural features which enable die segments
to be removed and replaced within the tray. However, to minimize
the number of different type parts required by the present system,
the opposing tray may be constructed identically to the master
tray, even though the frangible base and indexing grooves and ribs
are not required for the opposing cast, since it may remain
permanently affixed to the tray.
In any event, both the master and opposing trays, which may be of
identical construction, are provided with a hinge coupler bracket
which extends longitudinally outwards from a short end of each
tray. The bracket has the shape of a bifurcated L-bracket including
a flat longitudinally disposed horizontal floor plate which extends
perpendicularly outwards from a short vertical end wall of the
tray. The floor plate of the bracket has a flat horizontally
disposed upper surface which is recessed slightly below the upper
surface of the perimeter edge wall of the tray. A pair of
rectangularly-shaped connector plates protrudes upwardly from an
outer longitudinal end portion of the floor plate. The outer
connector plates from a pair of trays are releasably joined
together by a hinge coupler member that has an upper piano-type
hinge, and opposed horizontal upper support plates located on
opposite sides of a horizontally disposed hinge pin. The hinge
coupler has protruding perpendicularly downwardly from outer ends
of each support plate a vertical connector plate which has at the
lower end thereof a pair of inwardly facing C-shaped channel
members which have therein opposed vertically disposed C-shaped
channels adapted to insertably receive an outer upstanding end
plate of a tray coupler. This construction enables the outer
slotted ends of the hinge coupler to be readily slipped removably
over the upstanding connector flange plates of a longitudinally
aligned pair of trays, i.e., a master tray and an opposing tray,
and thereby hingedly coupling the two trays together so that upper
surfaces of the trays may be pivoted towards and away from one
another to simulate closure and opening of a patient's jaws.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded upper perspective view of a pair of trays and
a hinge coupler comprising components of pin tray dental prostheses
modeling system according to the present invention.
FIG. 2 is a side perspective view of the components of FIG. 1.
FIG. 3 is a lower plan view of the components of FIG. 1, with the
hinge coupler connected to the two trays.
FIG. 3A is an upper plan view of the hinge coupler of FIG. 3.
FIG. 4 is a perspective view showing a first step of a method for
making a modeling cast or "arch" from a single quadrant impression
mold made of a group of a patient's teeth located in either an
upper or lower jaw and including one or more teeth to be
renovated.
FIG. 5 is a perspective view of the arrangement of FIG. 4 showing a
second step in making a dental model cast from a single quadrant
impression.
FIG. 6 is a perspective view showing a completed master dental
model casting residing in a first tray in which it was cast, an
opposing cast positioned above the master cast with occlusal
surfaces of upper and lower replica teeth in the opposing and
master casts temporarily adhered together in proper occlusal
registration by blobs of wax, and the first, master tray coupled to
a second, opposing tray by a hinge coupler.
FIG. 7 is a view similar to that of FIG. 6, but showing semi-liquid
die stone applied to both the upper surface of the opposing cast,
and the upper surface of the opposing tray.
FIG. 8 is a view similar to that of FIG. 7, but showing the
opposing tray pivoted on the axis of the hinge coupler to thereby
bring the semi-liquid die stone material in the opposing tray and
the upper surface of the opposing casting into contact to thereby
comingle and cohere upon hardening, thus securing the opposing cast
to the opposing tray.
FIG. 9 is a perspective view showing a first step in a method of
making a master dental model cast and an opposing cast from master
and opposing impression molds made of teeth in opposite jaws of a
patient by a double-bite or "triple" impression tray.
FIG. 10 is a perspective view of a second step in fabricating
master and opposing articulated casts according to the present
invention.
FIG. 11 is a perspective view of a third step in the method of FIG.
10.
FIG. 12 is a perspective view of a fourth step of the double-tray
method of FIG. 10, as well as that the single tray method of FIGS.
4-8.
FIG. 13 is a perspective view of a fifth step in the double tray
method of FIG. 10, as well as the single tray method of FIGS.
4-8.
FIG. 14 is a perspective view of a sixth step in the double tray
method of FIG. 10, as well as the single tray method of FIGS.
4-8.
FIG. 15 is a perspective view of a seventh step in the double tray
method of FIG. 10, as well as the single tray method of FIGS.
4-8.
FIG. 16 is a perspective view of a completed articulatable model of
a pair of master and opposing dental modeling system casts
fabricated using the method and apparatus according to the present
invention.
FIG. 17 is a fragmentary view of the article of FIG. 16 on an
enlarged scale, showing a die segment thereof.
FIG. 18 is another fragmentary view of the article of FIG. 11 on an
enlarged scale, showing part of a master cast with the die segment
of FIG. 17 removed from the cast.
FIG. 19 is a perspective view of a knock-out template for removing
a frangible base plate of the tray shown in FIGS. 1-3.
FIG. 20A is a side elevation view of a knock-out tool useable with
the template of FIG. 19 to remove a frangible base plate from the
tray of FIGS. 1-3.
FIG. 20B is a side perspective view of the tool of FIG. 20A.
FIG. 21 is a perspective view of a sawing stand for use with the
method of the present invention.
FIG. 22 is a perspective view of a drilling alignment fixture
comprising a component for use in an alternative embodiment of a
pin tray dental prostheses modeling system according to the present
invention.
FIG. 23 is a perspective view of an alternative method for removing
a frangible base plate from a tray comprising a component of the
apparatus according to the present invention, without simultaneous
ejection of a dental model cast from the tray, as shown in FIG.
12.
FIG. 24 is a perspective view showing the tray of FIG. 23, with the
frangible base plate removed and slidably supported on the drilling
alignment fixture of FIG. 22.
FIG. 25 is a perspective view showing how the drilling jig of FIGS.
22 and 24 is used to guide drilling of pin bores into the base of
the dental model cast shown in FIGS. 23 and 24.
FIG. 26 illustrates one method for installing die segment pins in
pin bores formed in the dental model cast as shown in FIG. 25.
FIG. 27 illustrates one method for segmenting the dental model cast
of FIGS. 23-26 into individual die segments.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A. Drawing Description Summary
FIGS. 1-3 and 19-1 illustrate components of a basic embodiment of
dental prostheses modeling system according to the present
invention, while FIG. 22 illustrates a drilling alignment fixture
for use in an alternate embodiment of the system.
FIGS. 4-8 illustrate steps in a method of making a dental model
cast from a single quadrant impression for use in fabricating
dental prostheses, according to a basic embodiment of the
invention.
FIGS. 9-11 illustrate preliminary steps in making master and
opposing dental model casts from master and opposing mold
impressions made by teeth in upper and lower jaws of a patient, use
a "double-bite" or "triple" impression tray.
FIGS. 12-15 illustrate further steps in the method of fabricating a
dental prostheses model according to the present invention, from
either a single-bite or double-bite impression.
FIGS. 16-18 illustrate a finished pair of dental prostheses model
casts mounted in an articulator according to the present
invention.
FIGS. 23-27 illustrate steps in an alternative method for making
dental model casts according to the present invention.
B. Detailed Description
Referring now to FIGS. 1-3, an apparatus 30 for making pin-tray
dental prostheses models according to the present invention may be
seen to include a pair of molding trays 31A, 31B which are
releasably connectable by a hinge mechanism 32 and used for
fabricating and holding dental models made according to the present
invention. As shown in FIG. 16 and as will be described in detail
below, hinge mechanism 32 enables trays 31A, 31B to be pivoted
between a mutually co-planar horizontally disposition as shown in
FIG. 12, to a configuration in which one of the molding trays
overlies the other in a generally parallel disposition, as shown in
FIGS. 2 and 16.
As will be made clear in the ensuing description, only one of
molding trays 31A, 31B need by provided with certain novel
structural features according to the present invention, if a
removable dental model cast is to be made of teeth in a single jaw
of a patient. However, according to a preferred method of
practicing to the invention, trays 31A and 31B may be identical,
and for the sake of brevity in the ensuing description, the letter
suffix A or B is deleted unless necessary to distinguish between
two trays, e.g., a tray in which a master dental. cast is molded
versus a tray in which an opposing cast is molded.
As shown in FIGS. 1-3, each tray 31 has a longitudinally elongated
rectangular plan view shape. Tray 31 preferably has flat and
parallel upper and lower surfaces 33, 34, respectively. Also, tray
31 has longitudinally elongated, rectangularly shaped, vertically
disposed front and rear side walls 35, 36, a rectangularly shaped
inner (hinge side), vertical end wall 37 and an outer vertically
disposed end wall 38.
As shown in FIG. 1, tray 31 has formed in an upper part thereof of
a relatively shallow rectangularly-shaped depression or trough 39.
Trough 39 is concentric with the outer vertically disposed
perimeter wall surface 40 of tray 31, and is nearly as large as the
outer perimeter of the tray. Thus arranged, a thin
rectangularly-shaped peripheral ring 41 is formed between trough 39
and outer vertical perimeter wall surface 40 of tray 31. Peripheral
ring 41 around trough 39 has a flat, horizontally disposed base
wall 42. Peripheral ring 41 has disposed perpendicularly upwards
from the base wall 42 an inner peripheral wall 43 which has inner
wall surfaces, including front longitudinally disposed inner
surface 45, rear longitudinally disposed inner surface 46,and
shorter transverse end surfaces, i.e., left transverse inner
surface 47, and right transverse inner surface 48.
As shown in FIG. 1, front and rear inner wall surfaces 45, 46 of
peripheral ring 41 have formed therein a plurality of ribs 49 which
protrude inwardly towards a longitudinal center line of trough 39.
Ribs 49 protrude vertically upwardly of base wall 42, and form
between each adjacent pair of ribs a vertically disposed notch or
groove 50. As will be described in detail below, alternating ribs
and grooves 49, 50 form complementary grooves and ribs in outer
vertical surfaces of the base of a dental model cast formed in
trough 39 by solidified liquid die stone poured into the trough,
thus enabling the base and individual segments cut from the base,
to be removably returned to exact pre-existing locations within
tray 31, because of the indexing action of the ribs and grooves
being insertably received within complementary-shaped grooves and
ribs molded into the sides of the model cast by hardened liquid die
stone.
Referring now to FIGS. 1, 2, and 3, it may be seen that tray 31 is
provided with front and back or rear abutment flanges 55F, 55B,
which protrude outwardly from front and rear walls 35, 36,
respectively, of tray 31. As shown in the figures, each abutment
flange 55F, 55B has the shape of a horizontally disposed, thin,
longitudinally elongated rectangular rib or web which has an outer
vertical wall surface 56 that is spaced outwards from an outer
front or rear wall of tray 31, and flat and parallel, horizontally
disposed, upper and lower surfaces 57, 58, respectively. The
function of front and rear abutment flanges 55F, 55B are described
below.
Referring now to FIGS. 1 and 3, it may be seen that base wall 42 of
trough 39 in molding tray 31 has a flat upper surface 59, and
includes an outer rectangular ring-shaped portion 60 which is
joined to the inner wall surfaces of the front, rear, inner and
outer end walls of the tray. Base wall 42 also includes a
concentrically located, longitudinally elongated
rectangularly-shaped center panel 61. Base wall 42 has a thickness
of less than the height of tray 31, e.g., about 1/16 inch for a
tray height of about 7/16 inch, and upper surface 59 of base wall
42 is located about 1/16 inch below upper peripheral edge wall 33
of the tray. Thus arranged, base wall 42 forms within a lower
portion of tray 31 a relatively deep, e.g., about 3/8 inch, lower
upwardly concave opening or "matrix" trough 63 which protrudes
upwardly from lower peripheral face 64 of the tray.
Referring still to FIGS. 1 and 3, it may be seen that center panel
61 of base wall 42 is connected to outer rectangular ring-shaped
portion 60 of the base wall by a plurality of readily breakable, or
frangible members 65. Thus, as shown in FIG. 3, outer vertical wall
surface 66 of base wall center panel 61 is joined to inner vertical
wall surface 67 of ring-shaped portion 60 of the base wall by a
plurality of thin, breakable pins 65, e.g., a pair of front and
rear pins and a pair of left and right pins. In a preferred
embodiment, a tray 31 is fabricated as a unitary molded plastic
part, with outer surface 66 of center panel 61 angled downwardly
and. inwardly away from adjacent inner wall surface 67 of
ring-shaped outer portion 60 of base wall 42. With this
construction, pins 65 may be readily molded to have a thickness
substantially less than that of center panel 61, thus enabling the
pins to be readily broken and thereby permitting the center panel
to be broken away and removed from tray 31. With center panel 61
thus removed from tray 31, base wall 42 of the tray has through its
thickness dimension a concentrically located, longitudinally
elongated rectangular-shaped aperture 69 as shown in FIG. 23.
As shown in FIG. 3, center panel 61 of tray base wall 42 preferably
is provided with one or more bosses 70 which protrude
perpendicularly downwards from the lower surface 71 of the base
wall. Although the exact shape and size of bosses 70 is not
critical, the embodiment of tray 31 shown in FIG. 3 has three
square cross-section bosses 70 which each have a flat lower surface
72 and a blind circular bore 73 which extends perpendicularly
upwards from the lower surface. The three bosses 70 include a
longitudinally centrally located center boss 70C, and left (inner)
and right (outer) bosses 701L, 70R spaced equal longitudinal
distances away from the center boss. The function and purpose of
bosses 70 is described below.
Referring still to FIGS. 1, 2 and 3, it may be seen that each tray
31 has protruding horizontally outwards from a short end wall 37
thereof a hinge coupler bracket 74 for releasable attachment to
hinge mechanism 32. Each hinge coupler bracket 74 has a shape
approximating that of an L-bracket, an upright leg of which is
bifurcated into two spaced apart, parallel plates. Thus, as shown
in FIGS. 1-3, hinge coupler bracket 74 includes a
rectangularly-shaped base plate 75 which protrudes outwardly from
end wall 37 of tray 31. Base plate 75 has horizontally disposed
upper and lower surfaces 76, 77 which are parallel to upper surface
33 of tray 31. Upper surface 76 of bracket base plate 75 is
preferably recessed below upper surface 33 of the perimeter edge
wall of tray 31, and has protruding perpendicularly upwards
therefrom a first, outer rectangularly-shaped upright leg plate 78.
Outer upright leg plate 78 has an outer vertical surface 79 which
is co-planar with outer vertical edge wall 80 of a base plate
75.
Bracket 74 includes a second, inner upright leg plate 81 which is
shaped similarly to outer leg plate 78, and which protrudes
perpendicularly upwards from base plate 75 at a location spaced
longitudinally inwardly from the outer upright leg plate. Inner
upright leg plate 81 has an outer vertical wall surface 82 which is
spaced longitudinally inwards of and parallel to an inner vertical
wall surface 83 of outer leg plate 78. Preferably, a
rectangularly-shaped aperture 84 is formed through base plate 75 of
bracket 74, between outer and inner upright leg plates 78, 81. The
purpose of aperture 84 is to facilitate elastic flexure of the
outer and inner leg plates away from and towards one another,
thereby facilitating elastic gripping engagement of hinge mechanism
32, as will be described below.
Referring still to FIGS. 2, 3A, 3B, 6, and 7, it may be seen that
hinge mechanism 32 of apparatus 30 includes a pair of rectangular
plan-view hinge members 85, 86, each having a thin upper
rectangularly-shaped plate 87,88, respectively. Plate 87 has a pair
of spaced apart, coaxially tubular extensions 89,90, which protrude
upwardly from an inner end of the plate, parallel thereto. Plate 88
has a single, centrally located tubular extension 91 which fits
coaxially between tubular extensions 89, 90 of plate 87, and is
hingedly joined thereto by an elongated cylindrical hinge pin 91A
which is disposed rotatably through bores (not shown) of the
tubular extensions. The other parts of hinge members 85, 86 are
identical, and include a larger rectangularly-shaped coupler plate
92 which depends perpendicularly downwardly from outer edge 93 of
each upper plate. Coupler plate 92 has at opposite sides of a lower
horizontal edge wall 94 thereof a pair of vertically disposed,
L-shaped guide members 95 which form therebetween a pair of
vertically disposed C-shaped channels 95A which are adapted to
vertically upwardly insertably receive an inner upright leg plate
81 of a tray 31.
Each hinge member 85, 86 also has protruding laterally inwardly
from the L-shaped guide member 95 a vertically disposed lug member
96. Each lug member 96 has an inner vertical edge wall 97 which is
located parallel to and laterally spaced apart from an inner
vertical edge will 98 of coupler plate 92. As shown in FIG. 2,
inner facing edge walls 97 of lug members 96 abut to limit inward
pivotable motion of the coupler plates to a parallel position. As
shown in FIG. 3B, inner vertical edge wall 98 of each coupler plate
91 preferably has formed therein a plurality of parallel,
horizontally disposed, triangular cross-section ribs 100 which
alternate with grooves 101 to form a washboard-like surface 102.
The thickness of hinge coupler plate 92, measured between the
vertices of triangular webs 100 and outer surface 102 of the
coupler plate, is slightly greater than the spacing between an
inner and outer faces 83, 82 of outer and inner leg plate uprights
78, 81 of hinge coupler bracket 74 of tray 31. Thus, when coupler
plate 92 is inverted downwardly into the space 104 between the tray
upright leg plates, the latter flex elastically slightly apart, and
ribs 100 bite into the plates slightly, thus frictionally engaging
the coupler plate with the tray legs. A description of certain
components of a pin tray dental prostheses modeling system
according to the present invention having been given, the manner of
using those components according to methods of the present
invention is presented below.
FIG. 4 illustrates a first step in making a dental prostheses model
cast or "arch" from a single quadrant impression mold made of a
group of a patient's teeth located in an upper or lower jaw of the
patient. As shown in FIG. 4, the trough 39 in the upper portion of
a first molding tray 31A is fitted with a semi-liquid die stone
material L such as plaster of Paris, to a level slightly above
upper peripheral wall 33 of the tray. As is also shown in FIG. 4, a
dental impression mold A containing imprints B of a patient's teeth
is also filled to overflowing with liquid die stone. The filled
impression A is then inverted, positioned over tray 31A, and
pressed down onto the semi-liquid die stone in the tray, as shown
in FIG. 5. The semi-liquid die stone in impression A thus
co-mingles with that in tray 31A. Time is then allowed for the
liquid die stone in tray 31A to harden into a stone-like cast.
Next, impression mold A is peeled upwardly and off from the
hardened die stone in tray 31, leaving therein a cast C which is an
accurate replica of teeth which impressed or imprinted the
impression mold, as shown in FIG. 6.
Then, as shown in FIG. 6, a cast D made of an impression taken of
teeth opposing those which are to be restored and which imprinted
impression A is positioned above first, master cast C, which
replicates teeth for which prostheses are to be fabricated.
Opposing cast D is positioned in proper occlusal contact with
master cast C, and temporarily secured in that configuration by
blobs of wax E, for example, as shown in FIG. 6. Next, as shown in
FIG. 7, a second, opposed tray 31-B, coupled by hinge mechanism 32
to tray 31-A containing master dental model cast C, is filled to
overflowing with liquid die stone L, as is upper surface of
opposing cast D. Then, as shown in FIG. 8, the upper surface 33B of
opposing tray 31-B is pivoted towards contact with upper surface F
of opposing cast D, causing die stone in the upper impression to
co-mingle with that in the opposing tray. Time is once again
allowed for the liquid die stone in opposing tray 31-B and opposing
cast D to harden. Wax blobs E are then heated slightly to melt the
wax, enabling opposing tray 31-B, now secured to opposing cast D by
solidified die stone, to be pivoted away from master cast C.
Further processing steps used to complete pinned dental model cast
C are described below, following a description of preliminary steps
for making master and opposing casts from a double-bite, or triple
tray impression; the final steps of making finished casts are the
same for both single quadrant and triple tray impression casts.
FIGS. 9-11 illustrate a method of making dental model casts from
double-bite or triple-tray impressions according to the present
invention.
FIG. 9 shows a first step in making a dental prostheses model cast
from a double-bite or triple-tray impression mold G made from a
patient's teeth located in lower or upper jaw and including teeth
which are to be replaced by or fitted with one or more prosthetic
restorations or replacements, and occluding teeth in an opposing
jaw. As shown in FIG. 9, trough 39 in the upper portion of a first
molding tray 31-.alpha. is filled with a semi-liquid, hardenable
modeling substance L such as plaster of Paris or die stone, to a
level slightly above upper peripheral wall surface 33 of the tray.
As is also shown in FIG. 9, a concave depression in a first, master
side H of two-sided dental impression G imprinted with teeth which
are to be restored, is also filled to overflowing with liquid die
stone L. The filled master side impression H is then inverted,
positioned over tray 31-.alpha., and pressed down into the
semi-liquid die stone in the tray, as shown in FIG. 10. The
semi-liquid die stone in the impression H thus Co-mingles with
semi-liquid die stone material in tray 31-.alpha.. Time is then
allowed for the liquid die stone in tray 31-.alpha. and master
impression H to harden into a stone-like master cast J. Next,
liquid die stone L is poured to overflowing into a second, opposing
tray 31-.beta., which is pivotably connected to first tray
31-.alpha. by a hinge mechanism 32. As is also shown in FIG. 11, a
concave depression in second, opposing side K of two-sided
impression mold G imprinted with teeth in a jaw opposed to the jaw
containing teeth to be restored, is filled to overflowing with
liquid die stone L. As shown in FIG. 11, opposing tray 31-.beta. is
then pivoted towards contact with the upper surface of semi-liquid
die stone in concave impression area K of the opposing impression,
causing die stone in the upper, opposing impression to co-mingle
with die stone in the upper, opposing tray. Time is once again
allowed for the semi-liquid die stone in opposing tray 31-.beta.
and opposing impression K to harden into a stone-like opposing cast
L. Next, a master dental model cast J formed in master tray
31-.alpha. is temporarily and replacably removed from the tray, in
the following manner.
A preferred method for removing master dental model cast J from
tray 31-.alpha. consists essentially of exerting an upwardly
directed force on center panel 61 of base wall 42 of the tray which
is of sufficient strength to break pins 65 which join the center
panel to peripheral ring panel 60 of the base wall, and then
pushing upwardly on that portion of the lower surface M of a cast J
that is accessible through aperture 69 through the base wall.
According to a preferred method of removing cast J from tray
31-.alpha., a template 190 and tool 191, shown in FIGS. 1920A and
20B, are employed.
As shown in FIG. 19, template 190 includes a flat base 192 having a
longitudinally elongated, rectangular shape. Base 192 of template
190 has protruding perpendicularly upwards from a flat upper
surface 193 thereof a longitudinally elongated, rectangularly
shaped lug 194 which has a vertically disposed peripheral wall
surface 195 that is located concentrically with respect to the
outer peripheral wall surface 196 of the base, and has a flat upper
surface 197 disposed parallel to upper surface 193 of base 192.
Template 190 also includes at opposite short ends 198, 199 thereof
a pair of opposed, vertically disposed guide structures 200, 201
which have formed therein a pair of opposed inner facing C-shaped
guide spaces 202, 203 which together form an open
rectangular-shaped tray receipt space 204 which is concentric with
outer peripheral wall surface 195 of lug 194. As shown in FIGS. 12
and 19, tray receipt space 204 has a rectangular plan view shape
which is similar to that of tray 31, but of larger size so that the
tray may be loosely inserted downwardly into the space, the bottom
surfaces 72 of bosses 70 of base wall 41 abutting upper surface 197
of lug 194.
As shown in FIGS. 20A and 20B, a knock-out tool 191 according to
the present invention includes a rectangular block-shaped body 205
which has vertically elongated, rectangularly-shaped parallel left
and right side walls 206L, 206R and vertically elongated,
rectangularly-shaped parallel front and back side walls 207F, 207B,
which are perpendicular to the side walls. Body 205 has disposed
perpendicularly through left and right side walls 206L, 206R
thereof an arch-shaped tunnel 208. Body 205 of tool 191 has a flat,
horizontally disposed upper end wall 209, and a flat lower wall
surface 210. Tunnel 208 penetrates lower wall surface 210, thus
defining between front and back side walls 207F, 207B a pair of
front and rear legs 211F, 211B which have opposed lower, inner
vertical wall surfaces 212F, 212B which border the tunnel. Legs
211F, 211B each has at a lower end thereof a laterally disposed
rectangularly shaped foot flange 213F. 213B which has a flat lower
surface coextensive with lower wall surface 210 of body 205, and
flat, parallel upper surfaces 214F, 214B. Foot flanges 213F, 213B
protrude horizontally a short distance inwards into tunnel 208, and
have vertically disposed, inner facing parallel end walls 215F,
215B. Foot flange front and back end walls 215F, 215B are spaced
apart at a distance slightly greater than the space between the
outer surface of front and peripheral upper edge walls of tray
31.
FIG. 12 illustrates the use of template 190 and knock-out tool 191
to remove a dental cast J from tray 31-.alpha.. As shown in FIG.
12, tray 31-.alpha. containing cast J is placed in opening 204 of
template 190, with bottom surfaces 72 of bosses 70 supported on
upper surface 197 of lug 194. Knock-out tool 191 is then positioned
above front and back abutment flanges 55F, 55B of tray 31 with
lower surfaces of front and back knock-out tool flanges 213F, 213B
contacting the upper surfaces of the abutment flanges of the tray.
A sharp blow is then delivered downwardly to the upper surface of
the knock-out tool which causes the knock-out tool flanges to exert
a downward force on the tray abutment flanges, thus causing lug 197
to be pushed upwardly on center panel 61 of tray base wall 42,
breaking pins 65 which join the center panel to rectangular
ring-shaped portion 60 of the base wall, and thereby ejecting cast
J upwardly and out from the tray.
As shown in FIG. 13, a fifth step in making a dental prostheses
model according to the present invention consists of drilling blind
pin bores P into the base M of an inverted cast J, at locations
aligned with portions of the cast which are to be severed from
adjacent portions of the cast, to thereby form die segments which
are to be used as models for dental prostheses. Pin bores Pare also
drilled into locations of the base corresponding to portions of the
cast adjacent to die segments.
After pin bores P have been drilled into cast J as described above,
cylindrical metal pins 120 are inserted into the base. As shown in
FIG. 13, each pin has a short knurled end 121 and a longer smooth
shank 122. Pin bores P are drilled to a depth approximating the
length of knurled end 121 of pin 120, so that the smooth shank 122
protrudes perpendicularly downwards from lower face N of cast J.
Pins 120 are preferably secured in pin bores P by coating knurled
ends 121 of each pin with adhesive before inserting a pin into a
bore.
FIG. 14 illustrates a fifth step in making a dental prostheses
model according to the present invention. As shown in FIG. 14, a
release agent is applied to the outer surfaces of pins 120, cast J
is re-inserted into trough 39 of tray 31 and the tray is inverted.
A release agent is applied to lower face N of cast J, and liquid
die stone L is then poured into open lower portion 63 of the tray,
to a level between the lower end faces 123 of the pins, and the
lower peripheral rim 64 of the tray. Liquid die stone within the
lower portion is allowed to harden to form a rectangular
block-shaped, "stone matrix" 125, as shown in FIG. 18A. Cast J is
once again withdrawn from trough 39 of tray 31, a task which is
facilitated by exerting pressure on lower faces 123 of pins 120.
Then, as shown in FIG. 15, base M of pinned cast L is placed
upright in a horizontal channel 126 formed in the upper surface of
a sawing stand fixture 127 of the type shown in FIG. 21. A saw S is
then used to make vertical cuts T through cast J, on each side of a
portion of the cast which is to be used as die segment U for use as
a dental prostheses model. After one or more die segments U have
been severed from dental model cast J. the die segments and
adjacent portions of the cast may be repeatedly re-installed in
tray 31 at precisely indexed locations, owing to the interlocking
action of ribs and grooves of the cast engaging complementary
grooves and ribs in the inner side walls of tray 31. FIGS. 16, 17,
and 18 show a completed articulateable model of a master cast J
with replaceable die segments, and an opposing cast fabricated by
the above described apparatus and method according to the present
invention.
FIGS. 23-27 illustrate a modification of the apparatus and method
of the present invention described above. The modified apparatus
and method employ the first three steps described above for both
single quadrant and double-bite impression models. However, as
shown in FIG. 23, a fourth step in the modified method comprises
removing frangible center panel 61 of base wall 42 of tray 31 by
grasping a center panel boss 70 between the jaws V of a pliers W,
and exerting a pulling force sufficient to break center panel
support pins 65. Blind pin bores P are then drilled into the base M
of a cast J, in a manner described below, using a drilling
alignment fixture 130 of the type shown in FIG. 22.
As shown in FIG. 22, drilling alignment fixture 130 includes an
elongated, generally rectangular-shaped body 131 which has a flat
lower surface 132, and a flat upper surface 133 in which is formed
an elongated, shallow rectangular-shaped channel 134 which is
adapted to receive a tray 31 containing therein the base M of a
cast J.
Located in front and back sides of channel 134 are coplanar,
horizontally disposed flat front and back ledges 135F, 135B which
are of a proper spacing to support front and rear abutment flanges
55F and 55B of a tray 31.
Drilling alignment fixture 130 also includes a circular drill guide
bushing 136 fitted through a lower wall 137 of the fixture. An
index line 138 is inscribed on the outer surfaces of the fixture,
in longitudinal alignment with the center line of a coaxial bushing
136.
As shown in FIGS. 24 and 25, drilling alignment fixture 130 is used
by longitudinally sliding a cast J supported on ledges 135F, 135B
of the fixture to thereby position a location of the cast where it
is desired to insert a pin in longitudinal alignment with bushing
bore index line 138. Drilling alignment fixture 130 and cast J are
then rotated together as a unit to expose the lower surface 139 of
the fixture, whereupon a drill bit is inserted through bore 140 of
bushing 136, and rotated to drill a pin bore P at a desired
location into the base M of cast J. Next, as shown in FIG. 26, pins
120 are inserted into pin bores P made as described above. Then,
tray 31 containing cast J, is reoriented to an upright position, as
shown in FIG. 27, and vertical saw cuts T are made into the cast to
severe die segments from adjacent portions of the cast. Saw cuts T
are made downwards just to the upper surface levels of front and
back abutment flanges 55F, 55B. Cutting to the common level of the
upper surface of the abutment flanges ensures that the saw cuts are
made completely through the thickness of base M of cast J, thus
enabling a pinned die segment U to be removed from tray 31, as
shown in FIG. 18, and re-inserted into a precisely predetermined
position relative to adjacent segments of the cast, which need not
be removed, and repeatedly removed and re-inserted.
According to a first variation of the modified apparatus and method
described above and illustrated in FIGS. 23-27, after pin bores P
have been drilled into the base M of a cast J as shown in FIG. 25,
the cast may be ejected from a tray 31, as for example, using a
template 90 and knock-out tool as shown in FIG. 4. Then, pins 120
may be installed in the pin bores P of cast J in the manner
indicated in FIG. 13, and the remaining steps of the basic
embodiment of the method shown in FIGS. 13 through 15 and described
above performed to produce a completed dental prostheses model.
According to a second, slightly different variation of the modified
apparatus and method depicted in FIGS. 23-27, pins 120 may be
installed in bores P of cast J prior to ejecting the cast J from a
tray 31, whereupon the steps of the basic embodiment depicted in
FIGS. 14 and 18 and described above performed to produce a complete
dental prostheses model.
* * * * *